Fluorocarbon solvents, such as 1,1,2-trichloro-1,2,2-trifluoroethane, are widely used as degreasing agents due to their excellent solvent power for greases and some emulsion-type lubricants. Trichlorotrifluoroethane also finds wide use in removing solder flux from printed circuit boards due to its selective solvency and nonflammability. Since trichlorotrifluoroethane is non-polar, it does not remove polar contaminants. Thus, to overcome this inability, trichlorotrifluoroethane has, in the past, been mixed with aliphatic alcohols.
Alcohols, while being relatively poor solvents for oils, are good solvents for polar organic acids such as abietic acid which is one of the main constituents of resin flux formulations. Furthermore, monobasic alcohols such as methanol, ethanol isopropanol, etc., dissolve certain amounts of sodium chloride and potassium chloride, and mixtures thereof with trichlorotrifluoroethane serve as solvents for, among other things, removing fingerprints from contaminated substrates, such as glass.
Mixtures of trichlorotrifluoroethane and alcohols that exhibit a minimum boiling point, i.e., azeotropic mixtures, are not flammable and retain almost all of the safety characteristics of the fluorocarbon constituent.
The use of these solvents in vapor degreasing equipment is necessary because such systems generate redistilled material for final rinse-cleaning. The vapor degreasing system acts as a still. Therefore, unless a mixture of solvents exhibit a constant boiling point, i.e., are azeotropes or azeotrope-like, fractionation will occur and undesirable solvent distribution may act to upset the cleaning and safety of the processing. It is, therefore, advantageous to develop solvent mixtures which are azeotropes or azeotrope-like. Furthermore, the more alcohols that are present in the solvent mixtures the wider the spectrum of solvency power that the mixtures will have.
A number of azeotropic and azeotrope-like mixtures of trichlorotrifluoroethane with alcohols such as methanol, ethanol and isopropanol, with or without a third component such as nitromethane, have been disclosed. Several have been used commercially as degreasing solvents. For example, U.S. Pat. No. 3,903,009 discloses the ternary azeotrope of trichlorotrifluoroethane with nitromethane and ethanol; U.S. Pat. No. 3,960,746 dicloses azeotrope-like compositions comprising trichlorotrifluoroethane, methanol and nitromethane; U.S. Pat. No. 3,789,006 discloses the ternary azeotrope of trichlorotrifluorethane with nitromethane and isopropanol; U.S. Pat. No. 3,573,213 discloses the binary azeotrope of trichlorotrifluoroethane with nitromethane; U.S. Pat. No. 3,340,199 discloses the binary azeotrope of trichlorotrifluoroethane with isopropanol; L. H. Horsley [2152] Azeotropic Data-III (Am. Chem. Society 1973) discloses the binary azeotrope of trichlorotrifluorethane and ethanol; L. H. Horsley [1763] Azeotropic Data-III (Am. Chem. Society 1973) discloses the binary azeotrope of nitromethane and ethanol; L. H. Horsley [1781] Azeotropic Data-III (Am. Chem. Society 1973) discloses the binary azeotrope of nitromethane and isopropanol; and L. H. Horsely [1753] Azeotropic Data-III (Am. Chem. Society 1973) discloses the binary azeotrope of nitromethane and methanol.
There is a constant effort to develop similar solvents which have a greater versatility of solvent power.
It is the object of this invention to provide azeotropic or azeotrope-like solvent cleaning compositions which have good solvency power and versatility in solvent use.
This and other objects will become apparent from the description which follows.